1. Field of the Invention
The present utility model relates to the technical field of the collimation of X-rays, and in particular to a collimator and to CT (X-ray computed tomography) equipment comprising the collimator.
2. Description of the Prior Art
In CT equipment, when the X-rays are emitted from an X-ray tube, they need to be collimated via a collimator before being radiated onto a subject to be examined, and then they are received by a detector. The main function of the collimator is to limit the X-rays to be a fan beam in the Z direction and in a ψ plane, and to shield the X-rays in other directions. The collimator is critical in protecting the patients and operators from receiving excessive doses of radiation.
FIGS. 1 and 2 are schematic diagrams of part of the structure of CT equipment, in which FIG. 1 shows a schematic diagram of a cross section of the CT equipment in the YZ plane, and FIG. 2 shows a schematic diagram of a cross section of the CT equipment in the XY plane. As shown in FIGS. 1 and 2, the CT equipment has an X-ray tube 100, a collimator 200, a patient bed 300 and a detector 400. An X-ray beam 500 emitted from the X-ray tube 100, after being collimated by the collimator 200, passes through a patient 600 lying on the patient bed 300, and then arrives at the detector 400. After receiving the X-rays, the detector 400 converts the X-ray intensity into electrical signals and transmits them to an image reconstruction device for reconstructing a CT image. Since the present application mainly relates to the collimator 200, other components of the CT equipment are not shown in the figures.
In the currently available collimators, lead is mainly used as the shielding material. However, lead is toxic which may cause damage to human bodies or the environment. The currently available collimators have been provided with sufficient protecting measures, and will cause no harm to a human body or the environment during their practical operation. Nevertheless, there is a strong desire to reduce and even eliminate the use of lead in collimators.
Currently, the shielding materials complying with the safety standards (for example, “the restriction of the use of certain hazardous substances in electrical and electronic equipment” (RoHS) of European Union) are rather expensive. Moreover, since a collimator is disposed on a narrow rotational part of the CT equipment, it is very difficult to replace lead with a large amount of light metal (such as steel), because it is necessary to use a large amount of light metal to achieve the same shielding performance but there is no space to accommodate so much light metal on the small rotational part.
Published German patent application DE102007028231A1 by Siemens discloses a collimator, in which a tungsten plastic composite is used as the shielding material of the collimator.